upper radiatorhose pops off

[gbergae]

My upper radiator hose pops off after driving, stop and go, for 30 miles. the temp gauge always registered
in the normal range, and the engine never missed a beat!. While it was cooling, I checked the temp again, this time it was between the normal and the hot marks. I let it cool for an hour, slowly refilled with water through the upper hose, turned on the heat full, and made it home ( the same 30 miles). Previously, I had put a new Stant thermostat in, which I tested with a thermocouple in heating water on the stove.
My guess is my radiator is marginal, so I've ordered an aftermarket one, along with new gates hoses and a
radiator cap. Also, the barbed end of the radiator input tube broke off into the hose.. It's a'98 outback with
128k, and no (thanks to the Subaru God!), bubbles in the overflow tank (even at 2k rpm for 2 minutes).
Checked it this morning, and I haven't lost any water, and the car runs fine, although the upper hose is pretty hard!. Hope I'm right about the radiator!

[ouch1011]

I'm not sure I understand your post, but if the upper radiator hose keeps coming off, 1) its not clamped on tightly enough, 2) the hose is bad, or 3) the cooling system is overpressurizing. You mentioned something about the upper fitting being broken? If so that could also be the problem.

[gbergae]

Your're right, from what I've read, back pressure in the radiator (clogged from poor maintenance) causes
it to overpressurize on the hot side of the radiator. I would think this would cause the pressure cap to release,
but it didn't , the hose did. After the barb broke off, I filed down the little protrusion that limits how far back
on the radiator inlet pipe you can push the hose on it, and put on 2 band type clamps. I tightened them both
as much as I dared. Remember, I drove back home with the heat on, and it didn't pop off. Of course, this could have bled off any air in the system, if there was an air blockage. The temperature gauge was always in the normal range, never climbed. I bleed the system by revving the engine to 2k rpm for 5 minutes (subaru manual info). Do you think that the barbed end is important to make a positive seal? If so, my new radiator and hoses should solve the problem . Also, if it does work, would a botttle of water wetter in the coolant transfer the heat better?
I appreciate any input you could give me.

[jrg5066]

Hah, tis the season for popped off upper radiator hoses.

I think I may have poor maintenanced my radiator.

My radiator was previously puttied at the top hose inlet(or outlet). I cleaned all the old crud off and reputtied it the right way. Problem started when I took it on a test drive and the putty altho fully cured and hard as steel just would not hold on to the radiator. Pressure relieved from the seams where the putty contacted the radiator. So I went back to the drawing board and used the regular JB weld stuff and coated the putty + about 1" on all sides. I let it cure over night and in the morning I baked it out in the sun. There was no possible way ANYTHING was getting through that heap!! I installed the radiator serviced it, fired up the enigine with the cap off for about a minute and then finished off refilling the radiator. After capping it and reving for about 30seconds hissing and airbubbles startet coming out of a completely different place.

Did I do wrong? :smt012

[gbergae]

Hah, tis the season for popped off upper radiator hoses.

jb weld's max temperature is 500 degrees.You didn't do anything wrong, you just have other issues. You should probably bite the bullet and buy a new radiator ($100 from rock auto in madison,wi)....You might try bars stop leak in the silver tube . It's cheap ($3) and safe. It's a powder ( believe it or not , it's powdered ginger root!).

Put 1 tablespoon in a couple of ounces of warm water to dissolve the powder and pour it in the radiator. I don't suggest this is better than replacing the radiator, but you seem to be on a budget, and I've had good sucess with this over the years for "small hissing" leaks. It seems to stay in solution in the radiator until it finds a external passage to the air, then hardens. Good Luck!

[Huffer]

If your radiator is clogged, pressure is going to find the weakest point and escape that way.

Sealing up leaks isn't going to do any good if the coolant isn't allowed to flow through the rad as it was originally designed.

Drain the rad, unhook both upper and lower hoses, fire water through it from the top to see if any crud or leaks are appearing in the rad. Put a drain pan with a mesh screen so you can see if there was anything in it. If you see no leaks coming from anywhere, reattach the hoses and refill with coolant.

Make sure your bleeder valve is operational and your rad cap is on correctly.

[jrg5066]

Your're right, from what I've read, back pressure in the radiator (clogged from poor maintenance) causes
it to overpressurize on the hot side of the radiator. I would think this would cause the pressure cap to release,
but it didn't , the hose did. After the barb broke off, I filed down the little protrusion that limits how far back
on the radiator inlet pipe you can push the hose on it, and put on 2 band type clamps. I tightened them both
as much as I dared. Remember, I drove back home with the heat on, and it didn't pop off. Of course, this could have bled off any air in the system, if there was an air blockage. The temperature gauge was always in the normal range, never climbed. I bleed the system by revving the engine to 2k rpm for 5 minutes (subaru manual info). Do you think that the barbed end is important to make a positive seal? If so, my new radiator and hoses should solve the problem . Also, if it does work, would a botttle of water wetter in the coolant transfer the heat better?
I appreciate any input you could give me.
I'm deffinately sure a new radiator will fix it. The generic plastic parts in these radiators are just crud and will eventually give away at the clamps. The thing I'm afraid of is overpressurizing a new radiator and having to deal with leaks all over again.

When you bled the system by reving the engine to 2k rpm for 5 minutes did you leave anything uncapped to relieve the pressure? What is this bleeder valve? U mean the petcock drain at the bottom of the radiator?

[Reason]

Barb? :smt017 You mean the ribbed end?? If so then thats why it pops off. As the pressure builds and the water and coolant heats up that hose expands slightly. Mine broke off and did the same to me. No matter how titight I put it it popped off. I tighten it so much I cracked the whole damn thing. I had to make one good radiator from two bad ones and it's been holding ever since. I have a brand new Koyo radiator here collecting dust :-(

[gbergae]

I put in the new radiator, and everything seemed fine. Over several days, I drove the car without a hitch, but I had never driven the car more than 10 miles at a time. Last night (66 degree night)
I drove the car 30 miles round trip, mostly highway driving, temp gauge always registered normal, and as I pulled into the driveway, and idled for a minute or so, I noticed my cooling fans were on.
Is this normal? I wouldn't think on such a cool evening, they would, unless the car was already on the hot side. I'm going to wire up an l.e.d. to the fan relay so I can see if they come on at speed.
The upper hose (new) is tight and hot, the bottom (new), warm and not quite as tight. Lower temperature = lower pressure?
I've noticed that the radiator tubes are very narrow (1/8" high x 1/2" wide), but many rows (32?). Does even a new radiator have that much resistance to flow? Or am I noticing the differental
between the inlet and output of the water pump ("suck and push, warm and hot" to coin a phrase!).
Any thoughts on this would be appreciated.

[jey]

Normal for the fan to come on while idling. No air is moving across the radiator if you're just sitting there.

[gbergae]

Thanks, Jay. After running at normal speeds, and then idling, even a short time, it's bound to create a heat load. Is it unusual for Subaru owners to be paranoid?